Russian President Vladimir Putin said Kiev's operation in eastern Ukraine where government forces are fighting pro-Russian separatists around the cities of Donetsk and Luhansk is reminiscent of the World War Two Nazi siege of Leningrad.

"Small villages and large cities surrounded by the Ukrainian army which is directly hitting residential areas with the aim of destroying the infrastructure... It sadly reminds me the events of the Second World War, when German fascist... occupants surrounded our cities," Putin told a youth camp outside Moscow.